Answer to Question #131900 in Electricity and Magnetism for Manish

Question

 A charged rod is touched to a small metallic sphere placed at the origin. This is done at time t = 0. A sensitive field detector detects the electric fields at points 10 cm away and 50 cm away at time t = 1 nanosecond.

The expression of Coulomb’s law can match the measured value 

(a) at 10 cm point but not at 50 cm point

(b) at 50 cm point but not at 10 cm point

(c) both at 50 cm point and at 10 cm point

• (d) neither at 50 cm point nor at 10 cm point 

Answer 1

As per the question,

When charged rod is touched to the uncharged small metallic sphere, then charge will start to transfer from higher potential body to the lower potential body and Both body will have at the same potential. So smaller sphere will get charged.

So after 1 nano second, charge will get transfer on the sphere.

Hence as per the coulomb's law, charged body generates a electric field

Which is $\overrightarrow{E}=\frac{Q}{4\pi \epsilon_o r^2}$

Hence, both at 50cm and 10cm will detect electric field.

Hence correct answer is option (c)

Condition II: If body charged is not touched to uncharged sphere, then charge will get induced in the sphere and if the charged rod will remove then, induced charge will also dis appear, hence in this condition it will not generate any electric field.